In conclusion, we propose that detecting changes in immune cell subsets can predict clinical outcomes when combined with other parameters, such as pathogenic, likely pathogenic, or VUS mutations in specific genes, including KRAS, KEAP-1, STK-11, NOTCH-1, and TP53. Our study is one of the few prospective studies in which pre-treatment analysis of immune cell subsets in the blood is compared with post-treatment cycles using flow cytometry and NGS of the tumor tissue from the same patient to predict the clinical response to PD-1 blockade. The gene discussed is KRAS; the disease is neoplasm.